Apparatus and equipment such as, for example, internal combustion engines, compressors and poppet valves emit pressure pulses and flow pulses in their exhausts. In certain of the apparatus and equipment, such as the internal combustion engines, products of combustion comprise the flow pulses. The pressure and flow pulses are sources of noise, and the flow pulses can create a back pressure that adversely affects the operational efficiency of the apparatus and equipment.
The known exhaust systems that are employed with the aforementioned sources of pressure and flow pulses for the purpose of receiving and conveying away from the sources the pressure pulses and exhaust products that are emitted as flow pulses are varied. In many cases the designs of such exhaust systems do not adequately account for the back pressure that can be created by the flow pulses nor do the systems regulate the pressure pulses in a manner to improve the operational efficiency of the sources of the pressure pulses.
In particular, it is often the case that the known exhaust systems are intended to muffle, or attenuate, the undesirable noise generated by the operation of the sources of pressure and flow pulses. The energy of the pressure pulses is the primary source of such noise. Not only are the pressure pulses audible in and of themselves, in addition, pressure pulses reflect off obstructions and surfaces generating additional frequencies, often sinusoidal in nature, which are perceived as secondary noise. Also, should flow pulses pass over an obstruction, an intensified pressure field is formed on the upstream side of the obstruction and a reduced pressure field is formed on the downstream side of the obstruction. These pressure fields cause the generation of additional secondary noise of a generally sinusoidal nature having differing frequencies. Numerous devices are known to those skilled in the art for attenuating the secondary noise. However, the wave lengths of the secondary noise typically are such that the attenuating devices necessarily contain multiple chambers and passages, particularly where wave cancellation techniques are employed to attenuate the noise, and, as a result, are undesirably large and cumbersome. Such devices, as well as noise muffling devices that employ baffling or expansion techniques, often restrict exhaust flow by not adequately taking into account the flow pulses that are generated and, consequently, an undesirable back pressure is created at the location where the exhaust products are emitted. As a result, the operational efficiency of the source of the flow pulses is negatively affected. Additionally, the known devices do not regulate the pressure pulses in way that improves the operational efficiency of the sources of the pressure pulses.